Electronic fuel injection systems require accurate electronic means for opening and closing the fuel injector valves over a wide range of engine speeds. Maximum efficiency of the engine requires the best possible mixture of air and fuel at any given engine speed. The necessary open time for the injector valve at any given speed can be determined within fairly precise limits to reduce the chances of hydrocarbon pollution. However, the open time is dependent not only on the speed of the engine, but also on water temperature, air temperature, and other conditions of the environment. Experiments have shown that there is no simple mathematical relationship of the valve open time with respect to engine speed. However, it has been determined that satisfactory operation is obtained if the open time of the valve is changed for different portions of the speed range within the wide range of operating speeds which may be used. To provide the changes in open time for the various speeds requires a relatively complex control system which tends to be expensive.